For controlling vehicle doors in the field of public passenger transport, for example, in busses, trams or trains, the use of pneumatic or electropneumatic control systems is known. The control system contains as a drive one or more pneumatic working elements with pressure chambers for producing an opening and/or closing force for the vehicle door. Generally, two pressure chambers, an opening chamber and a closing chamber, are associated with the vehicle door. In this instance, it is possible to use as a drive, for example, a dual-action working or actuation cylinder. In order to open or close the doors, the respective pressure chamber of the working or actuation cylinder is acted on with pressure and the other chamber is ventilated in each case. Technical considerations of operational safety and legal regulations require at the same time the possibility of manual capacity for emergency operation of the vehicle doors in the event of malfunctions.
DE 32 25 536 A1 discloses a pneumatic vehicle door control system with a dual-action working cylinder and an electropneumatic control device whose chambers can be connected by means of upstream electrically switchable 3/2-way solenoid valves in each case in an opposing manner to a compressed air source or ventilation outlets of the 3/2-way solenoid valves. The 3/2-way solenoid valve arranged upstream of the opening chamber can be switched by means of a manually operable emergency tap, shuttle valve and an additional chamber which can be aerated by the compressed air source from the aeration position into the ventilation position. For complete ventilation of the system, the other 3/2-way solenoid valve can if necessary at the same time be electrically switched into the ventilation state. The pneumatic control system disclosed in DE 32 25 536 A1 further provides for electrical safety circuits of the 3/2-way solenoid valves in accordance with the differential pressure principle if defined pressure values are exceeded at specific locations of the system as a result of operational malfunctions. The emergency shutdowns provided in accordance with DE 32 25 536 A1 require for complete ventilation of the system depending on the current operating state either an active switching of involved components by means of a hand-operable emergency tap or additionally by means of an electronic switching device. The control system does not consequently enable any complete independent ventilation of the working cylinder in the event of a failure or a shutdown of the compressed air source. Furthermore, a complete ventilation in the event of failure of the electrical supply is not ensured. In addition, the vehicle door control provided by DE 32 25 536 A1 is relatively complex as a result of the large number of provided emergency shutdown functions.
DE 34 20 631 A1 discloses a pneumatic vehicle door control with a dual-action working cylinder whose chambers can be connected by means of upstream 3/2-way valves in each case in an opposing manner to a compressed air source or ventilation outlets of the 3/2-way solenoid valves. The two 3/2-way valves can be switched by means of three different electromagnetically, pneumatically and mechanically controllable actuation devices. For emergency control, a third, electromagnetically switchable 3/2-way valve and a manually operable emergency tap are provided. The control of the electromagnetic actuation members is carried out by means of a central electronic switching device. The vehicle door control proposed by DE 34 20 631 A1 provides—in a manner comparable with DE 32 25 536 A1—several relatively complex emergency shutdown functions which can be activated by means of monitoring devices which are constructed as differential pressure switches or by means of manual activation using a switch or the emergency tap and therefore has the same disadvantages as the vehicle door control system known according to DE 32 25 536 A1.
DE 196 457 01 A1 discloses a pneumatic door control system having a dual-action working cylinder whose chambers can be connected by means of upstream pneumatically switchable 3/2-way solenoid valves in an opposing manner to a pressure medium inlet or a pressure medium outlet, wherein the switching of the two 3/2-way valves is carried out by means of three electrically switchable solenoid precontrol valves. The pneumatic door control provides for a safety switching state in which as a result of the actuation of one of the three solenoid precontrol valves both chambers of the working cylinder are connected by means of a corresponding identical positioning of the 3/2-way valves to the pressure medium inlet and are acted on at the same time, whereby an assumed position of the vehicle door is secured. The door control system disclosed by DE 196 457 01 does not provide for any simultaneous ventilation of both chambers of the working cylinder. Furthermore, a failure of the electrical supply leads to the failure of the control system, whereby the working cylinder remains in its current operating state.
DE 10 2008 011 315 A1 discloses a pneumatic vehicle door control system having a dual-action working cylinder whose chambers can be connected by means of upstream pneumatically switchable 3/2-way valves to a compressed air source, wherein the 3/2-way valves connect both chambers in an idle position to the compressed air source and the control pressure for one of the two 3/2-way valves is based on the pressure of the other chamber of the working cylinder. In one embodiment, the 3/2-way valves are resiliently pretensioned into the idle position. In order to prevent a sudden opening and closure of the doors, there are arranged upstream of the chambers of the working cylinder, upstream of the 3/2-way valves, parallel circuits comprising non-return valves which block the return flow and throttles which act as exhaust air throttles. The vehicle door control system disclosed by DE 10 2008 011 315 A1 does not provide for any manual capacity for emergency operation of the vehicle doors with a ventilation of the chambers of the working cylinder in the event of malfunctions.
DE 2011 001 003 A1 discloses a pneumatic vehicle door control with a dual-action working cylinder whose chambers can be connected by means of upstream electrically and manually controllable 3/2-way valves to a compressed air source, wherein the 3/2-way valves apply pressure to both chambers in a preferably spring-loaded idle position and secure the working cylinder in the position which it has assumed. The 3/2-way valves can be moved by means of electrically controllable actuators or by means of manual activation into a ventilation position, in which the chamber which is associated therewith in each case is ventilated, whereby an opening or closing of the vehicle doors is brought about. In order to prevent sudden opening and closing of the doors, there are arranged upstream of the chambers of the working cylinder, upstream of the 3/2-way valves, parallel circuits comprising non-return valves which block the return flow and throttles which act as exhaust air throttles. In the case of a drop in the electrical line supply, the control system according to DE 2011 001 003 A1 provides for a manual emergency activation of the vehicle doors by means of the manual movement of a hand-operated valve which is arranged downstream of the compressed air source into a ventilation position in which the system is separated from the compressed air source and is connected by means of a shuttle valve which is also activated by the hand-operated valve to a rapid ventilation, whereby both chambers are ventilated. The vehicle door control system which is provided in accordance with DE 2011 001 003 A1 requires for complete ventilation the operation of a hand-operated valve which potentially cannot be reached in every emergency situation. The control system further does not enable any complete independent ventilation of the working cylinder in the event of a failure or a shutdown of the compressed air source. Since the parallel circuits which act as an exhaust air throttle are arranged directly upstream of the chambers of the working cylinder, they also act during manual emergency operation, whereby an increased opening or closing resistance exists with manual emergency operation.